There are also differences among types of tea. Historically, white teas have been considered more delicate and gentle than the other teas. At Amsterdam Teas, we, too, appreciate the gentle character of white teas – but while studies have borne out that white teas tend to lower caffeine levels, the differences can be small, and the caffeine content of any given white tea will inevitably vary. Oolongs, which go through a complex variety of steps including multiple stages of oxidation, and which exhibit incredible variety one from another as a result, have also tended to show relatively lower caffeine content in testing.
Some differences in caffeine content across types of tea have to do with the oxidation process. Oxidation has two contrary effects on caffeine in tea. On the one hand, oxidation will reduce the total amount of caffeine in tea, but only by a relatively small amount. On the other hand, oxidation will loosen somewhat the bonds between caffeine and tannins. Plus, we tend to steep black teas at higher temperatures than other teas, which can have a marginal effect on the amount of caffeine that dissolves in liquid. The result is that the caffeine from a highly oxidized leaf of black tea will release relatively more quickly into the cup and body than caffeine from a green tea, as green teas have been prevented from oxidizing and tend to steep at lower temperatures.
In addition, it is worth keeping in mind that teas with ingredients that do not contain caffeine will yield a cup with less caffeine. Thus our genmaicha, for instance, which is a green sencha mixed with toasted rice, will contain a relatively small amount of caffeine. Likewise our ginseng oolong, which is an oolong tea coated in a shell of powdered oolong.
Herbal teas, as a rule, do not have any caffeine at all. As of this writing, our herbals include rooibos, chamomile and brandnetel (or nettle), all of which contain no caffeine. Some studies have found trace amounts of caffeine in the linden blossom, another of our herbal teas, but the amount detected has been negligible by comparison with tea and coffee.
We hope this helps to explain what theïne is and does, and how caffeine in tea varies from caffeine in coffee – why it is milder and less physical – as well as the sort of lift that you can expect from a cup of tea. Enjoy your next pot!